There have been two general approaches to making catalytic exhaust converters for automobiles and other motor vehicles. One has involved the use of a loose bed of ceramic pellets as a carrier for the catalyst, and the other has involved the use of rigid ceramic elements as the catalyst carrier. The bed of ceramic pellets has the disadvantage of attrition of the pellets due to self-abrasion so that the bed has to be replaced at relatively frequent intervals, while the use of rigid ceramic carriers has the disadvantage of inadequate resistance to thermal shock and to mechanical shock.
More recently the rigid type of ceramic carriers have been made from retriculated tubes of reinforced ceramic fibers which provide adequate resistance to both thermal shock and mechanical shock.
U.S. Pat. No. 4,092,194 and U.S. Pat. No. 3,986,528 disclose a reticulated tube of reinforced ceramic fibers suitable for use as a catalyst carrier for use in the catalytic conversion of internal combustion engine exhaust fumes. The tube is comprised of multiple layers of continuous yarn of ceramic fibers bonded, if desired, with a non-porous binder and contained in a refractory oxide matric suitable for use as a catalyst support.
U.S. Pat. No. 3,949,109 discloses a catalyst for use in fixed bed flow reactors comprising a porous, self-supporting structure of multiple layers of partially sintered glass-ceramic fibers. The structure preferably is tubular and has diamond shaped apertures in its walls to provide good fluid permeability. When coated with a catalyst, the structures are particularly useful in the catalytic conversion of pollutants in the exhaust fumes of internal combustion engines.
U.S. Pat. No. 3,645,833 discloses a quasi-isotropic sandwich-type structural core filament winding made on a jig on which the filaments ar interwoven in a . manner where each fiber lays on top of the preceding fiber so that when the winding is completed, a core is produced which consists of a series of tetrahedrons, half of which point upwards and half point downwards. The jig may be of varied shapes so that the core is flat, cylindrical, air foil or other irregular shapes.
U.S. Pat. No. 4,509,702 discloses an apparatus method and package for winding strands to achieve good split efficiency on removal of the plurality of strands from the package for further processing. The apparatus has fiber forming means, means for applying chemicals such as lubricants or binders to the fibers, means to gather the fibers into a plurality of strands, a rotatable winder to wind the strands and a slotted traversing guide. The traversing guide has more than one slot to guide the strands. The slots are disposed perpendicularly to the axis of rotation of the winder.